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Tuesday, May 11, 2010

Rods, Cones, and Galaxies

When I was in elementary school, my class took a field trip to a planetarium (which, at the time, sounded to me like it ought to be an aquarium for plants). With her laser pointer, the instructor indicated a cluster of stars on the ceiling. She said it was easier to see if you focused your eyes a little off to the side. This mystified me. Why on earth--or not, I guess--would you ever be able to see something more clearly by not looking at it?!

This cluster of stars might be the Triangulum Galaxy, based on a few quick Google-searches. I'm not sure, though, and I wish I'd paid closer attention to that presentation years ago. The night sky continues to fascinate me, and I love to spot constellations and galaxies, planets and stars whose names I know. My little brother and I once spent some time on the hood of my car outside, looking at what constellations we could see through the trees. The sky is a symbol of hope, wonder, the unknown, the future, the past, and it's also an art display, a free light show that everyone can see all at once, and it's not exactly the same in any two places. Have you ever looked out and wondered who else might be doing the exact same thing, maybe not just on this planet?

That galaxy seemed to possess this weird, magical, unexplainable quality. It was surely some space-magic that made it easier to find out of the corner of your eye. Wasn't it? Some otherworldly, starry, extraterrestrial pixie dust that played tricks on your eyes or brain or whatever. I think a small part of me believed that aliens were controlling my mind from that far away and had some hi-tech cloaking device that hid their entire galaxy from view when any earthling stargazer tried to look directly at it.

Today in physics class we talked about eyes and electromagnetic waves. Colors, light, radios, and microwaves were all part of the docket. We performed a couple of labs involving color and optical tricks, after images, diffraction of light through an opening, and doing exactly what your mother told you not to do while watching TV--getting so close to it you can see the little colored lights.

Then we discussed the nerve endings in the eye that perceive color, and along with them, the ones that perceive light. Cones and rods, respectively. As it turns out, we have more cones in the center of our eyes, and a higher concentration of rods on the edges. For this reason, it is often difficult for us to determine color when viewing objects in the periphery. (I've never noticed this, but I wear glasses, so my peripheral vision is pretty useless as is.) The other thing it means is that we are better at seeing dimmer lights at the edges of our field of vision.

I should have been thrilled to hear this. Finally, a (literally) galactic mystery solved! The aliens had been foiled, and the secret of their cloaking device unveiled!

But I was disappointed. Being a logically-oriented person, I usually analyze and seek an answer from everything I ever come in to contact with. This answer, however, I rejected. I mean, I didn't actually refuse to believe it, but it was an unwelcome solution to a familiar mystery. Like the ancient Greeks, unable to explain sea foam, decided it was Poseidon's horses, pulling his chariot through the water. It's absurd, but it's a lot more interesting than entrapped gasses, as are aliens than light receptors in the eye.

Now, it's probably a good thing that someone, somewhere, knows the right answer. But there are some things I'd rather leave a mystery. I'd also like to point out that just because we do have more rods than cones on the edges of our retinas, it doesn't mean there aren't aliens in the Triangulum Galaxy. And maybe they have theories about the Milky Way. And maybe they're wrong.